1. Field of the Invention
The present invention relates to a rotor of an induction motor, and more particularly, to a rotor of an induction motor with end ring assemblies formed by electron beam welding or laser welding.
2. Description of the Prior Art
A rotor of an induction motor generally comprises a shaft and a laminated magnetic core mounted to the shaft. The laminated magnetic core is formed with a plurality of slots for allowing a plurality of conductive bars to pass through. The conductive bars extend out of both ends of the laminated magnetic core, and an end ring or end cap at either end of the laminated magnetic core is configured to mechanically and electrically connect to the conductive bars.
In one well known method of rotor production, the conductive bars and the end rings are integrally formed by casting. However, the conductive bars may shrink after formation, such that the conductive bars are loose in the slots. In addition, bubbles may form in structures of the conductive bars and the end rings, and layers of insulation material on surfaces of the laminated magnetic core may be damaged during the casting process. The prior art provides several techniques for solving the above problem by forming the conductive bars and the end rings (or end caps) separately. For example, US patent application number 2014/0339950 discloses a rotor assembly with end caps welded to conductive bars by electron beam welding. However, the end caps are formed by forging, which requires more complex manufacturing processes. Moreover, each of the conductive bars is welded to the end cap at one single position, thus connection reliability between the conductive bars and the end caps may not be sufficient for long term operation.